/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 *
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @since 1.2.2
 */
public abstract class ReflectionUtils {

   /**
    * Attempt to find a {@link Field field} on the supplied {@link Class} with the
    * supplied <code>name</code>. Searches all superclasses up to {@link Object}.
    * @param clazz the class to introspect
    * @param name the name of the field
    * @return the corresponding Field object, or <code>null</code> if not found
    */
   public static Field findField(Class<?> clazz, String name) {
      return findField(clazz, name, null);
   }

   /**
    * Attempt to find a {@link Field field} on the supplied {@link Class} with the
    * supplied <code>name</code> and/or {@link Class type}. Searches all superclasses
    * up to {@link Object}.
    * @param clazz the class to introspect
    * @param name the name of the field (may be <code>null</code> if type is specified)
    * @param type the type of the field (may be <code>null</code> if name is specified)
    * @return the corresponding Field object, or <code>null</code> if not found
    */
   public static Field findField(Class<?> clazz, String name, Class<?> type) {
//      Assert.notNull(clazz, "Class must not be null");
//      Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified");
      Class<?> searchType = clazz;
      while (!Object.class.equals(searchType) && searchType != null) {
         Field[] fields = searchType.getDeclaredFields();
         for (Field field : fields) {
            if ((name == null || name.equals(field.getName())) && (type == null || type.equals(field.getType()))) {
               return field;
            }
         }
         searchType = searchType.getSuperclass();
      }
      return null;
   }

   /**
    * Set the field represented by the supplied {@link Field field object} on the
    * specified {@link Object target object} to the specified <code>value</code>.
    * In accordance with {@link Field#set(Object, Object)} semantics, the new value
    * is automatically unwrapped if the underlying field has a primitive type.
    * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}.
    * @param field the field to set
    * @param target the target object on which to set the field
    * @param value the value to set; may be <code>null</code>
    */
   public static void setField(Field field, Object target, Object value) {
      try {
         field.set(target, value);
      }
      catch (IllegalAccessException ex) {
         handleReflectionException(ex);
         throw new IllegalStateException("Unexpected reflection exception - " + ex.getClass().getName() + ": "
               + ex.getMessage());
      }
   }

   /**
    * Get the field represented by the supplied {@link Field field object} on the
    * specified {@link Object target object}. In accordance with {@link Field#get(Object)}
    * semantics, the returned value is automatically wrapped if the underlying field
    * has a primitive type.
    * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException(Exception)}.
    * @param field the field to get
    * @param target the target object from which to get the field
    * @return the field's current value
    */
   public static Object getField(Field field, Object target) {
      try {
         return field.get(target);
      }
      catch (IllegalAccessException ex) {
         handleReflectionException(ex);
         throw new IllegalStateException(
               "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
      }
   }

   /**
    * Attempt to find a {@link Method} on the supplied class with the supplied name
    * and no parameters. Searches all superclasses up to <code>Object</code>.
    * <p>Returns <code>null</code> if no {@link Method} can be found.
    * @param clazz the class to introspect
    * @param name the name of the method
    * @return the Method object, or <code>null</code> if none found
    */
   public static Method findMethod(Class<?> clazz, String name) {
      return findMethod(clazz, name, new Class[0]);
   }

   /**
    * Attempt to find a {@link Method} on the supplied class with the supplied name
    * and parameter types. Searches all superclasses up to <code>Object</code>.
    * <p>Returns <code>null</code> if no {@link Method} can be found.
    * @param clazz the class to introspect
    * @param name the name of the method
    * @param paramTypes the parameter types of the method
    * (may be <code>null</code> to indicate any signature)
    * @return the Method object, or <code>null</code> if none found
    */
   public static Method findMethod(Class<?> clazz, String name, Class<?>... paramTypes) {
//      Assert.notNull(clazz, "Class must not be null");
//      Assert.notNull(name, "Method name must not be null");
      Class<?> searchType = clazz;
      while (searchType != null) {
         Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
         for (Method method : methods) {
            if (name.equals(method.getName())
                  && (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes()))) {
               return method;
            }
         }
         searchType = searchType.getSuperclass();
      }
      return null;
   }

   /**
    * Invoke the specified {@link Method} against the supplied target object with no arguments.
    * The target object can be <code>null</code> when invoking a static {@link Method}.
    * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
    * @param method the method to invoke
    * @param target the target object to invoke the method on
    * @return the invocation result, if any
    * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
    */
   public static Object invokeMethod(Method method, Object target) {
      return invokeMethod(method, target, new Object[0]);
   }

   /**
    * Invoke the specified {@link Method} against the supplied target object with the
    * supplied arguments. The target object can be <code>null</code> when invoking a
    * static {@link Method}.
    * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
    * @param method the method to invoke
    * @param target the target object to invoke the method on
    * @param args the invocation arguments (may be <code>null</code>)
    * @return the invocation result, if any
    */
   public static Object invokeMethod(Method method, Object target, Object... args) {
      try {
         return method.invoke(target, args);
      }
      catch (Exception ex) {
         handleReflectionException(ex);
      }
      throw new IllegalStateException("Should never get here");
   }

   /**
    * Invoke the specified JDBC API {@link Method} against the supplied target
    * object with no arguments.
    * @param method the method to invoke
    * @param target the target object to invoke the method on
    * @return the invocation result, if any
    * @throws SQLException the JDBC API SQLException to rethrow (if any)
    * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[])
    */
   public static Object invokeJdbcMethod(Method method, Object target) throws SQLException {
      return invokeJdbcMethod(method, target, new Object[0]);
   }

   /**
    * Invoke the specified JDBC API {@link Method} against the supplied target
    * object with the supplied arguments.
    * @param method the method to invoke
    * @param target the target object to invoke the method on
    * @param args the invocation arguments (may be <code>null</code>)
    * @return the invocation result, if any
    * @throws SQLException the JDBC API SQLException to rethrow (if any)
    * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
    */
   public static Object invokeJdbcMethod(Method method, Object target, Object... args) throws SQLException {
      try {
         return method.invoke(target, args);
      }
      catch (IllegalAccessException ex) {
         handleReflectionException(ex);
      }
      catch (InvocationTargetException ex) {
         if (ex.getTargetException() instanceof SQLException) {
            throw (SQLException) ex.getTargetException();
         }
         handleInvocationTargetException(ex);
      }
      throw new IllegalStateException("Should never get here");
   }

   /**
    * Handle the given reflection exception. Should only be called if no
    * checked exception is expected to be thrown by the target method.
    * <p>Throws the underlying RuntimeException or Error in case of an
    * InvocationTargetException with such a root cause. Throws an
    * IllegalStateException with an appropriate message else.
    * @param ex the reflection exception to handle
    */
   public static void handleReflectionException(Exception ex) {
      if (ex instanceof NoSuchMethodException) {
         throw new IllegalStateException("Method not found: " + ex.getMessage());
      }
      if (ex instanceof IllegalAccessException) {
         throw new IllegalStateException("Could not access method: " + ex.getMessage());
      }
      if (ex instanceof InvocationTargetException) {
         handleInvocationTargetException((InvocationTargetException) ex);
      }
      if (ex instanceof RuntimeException) {
         throw (RuntimeException) ex;
      }
      handleUnexpectedException(ex);
   }

   /**
    * Handle the given invocation target exception. Should only be called if no
    * checked exception is expected to be thrown by the target method.
    * <p>Throws the underlying RuntimeException or Error in case of such a root
    * cause. Throws an IllegalStateException else.
    * @param ex the invocation target exception to handle
    */
   public static void handleInvocationTargetException(InvocationTargetException ex) {
      rethrowRuntimeException(ex.getTargetException());
   }

   /**
    * Rethrow the given {@link Throwable exception}, which is presumably the
    * <em>target exception</em> of an {@link InvocationTargetException}. Should
    * only be called if no checked exception is expected to be thrown by the
    * target method.
    * <p>Rethrows the underlying exception cast to an {@link RuntimeException} or
    * {@link Error} if appropriate; otherwise, throws an
    * {@link IllegalStateException}.
    * @param ex the exception to rethrow
    * @throws RuntimeException the rethrown exception
    */
   public static void rethrowRuntimeException(Throwable ex) {
      if (ex instanceof RuntimeException) {
         throw (RuntimeException) ex;
      }
      if (ex instanceof Error) {
         throw (Error) ex;
      }
      handleUnexpectedException(ex);
   }

   /**
    * Rethrow the given {@link Throwable exception}, which is presumably the
    * <em>target exception</em> of an {@link InvocationTargetException}. Should
    * only be called if no checked exception is expected to be thrown by the
    * target method.
    * <p>Rethrows the underlying exception cast to an {@link Exception} or
    * {@link Error} if appropriate; otherwise, throws an
    * {@link IllegalStateException}.
    * @param ex the exception to rethrow
    * @throws Exception the rethrown exception (in case of a checked exception)
    */
   public static void rethrowException(Throwable ex) throws Exception {
      if (ex instanceof Exception) {
         throw (Exception) ex;
      }
      if (ex instanceof Error) {
         throw (Error) ex;
      }
      handleUnexpectedException(ex);
   }

   /**
    * Throws an IllegalStateException with the given exception as root cause.
    * @param ex the unexpected exception
    */
   private static void handleUnexpectedException(Throwable ex) {
      throw new IllegalStateException("Unexpected exception thrown", ex);
   }

   /**
    * Determine whether the given method explicitly declares the given
    * exception or one of its superclasses, which means that an exception of
    * that type can be propagated as-is within a reflective invocation.
    * @param method the declaring method
    * @param exceptionType the exception to throw
    * @return <code>true</code> if the exception can be thrown as-is;
    * <code>false</code> if it needs to be wrapped
    */
   public static boolean declaresException(Method method, Class<?> exceptionType) {
//      Assert.notNull(method, "Method must not be null");
      Class<?>[] declaredExceptions = method.getExceptionTypes();
      for (Class<?> declaredException : declaredExceptions) {
         if (declaredException.isAssignableFrom(exceptionType)) {
            return true;
         }
      }
      return false;
   }

   /**
    * Determine whether the given field is a "public static final" constant.
    * @param field the field to check
    */
   public static boolean isPublicStaticFinal(Field field) {
      int modifiers = field.getModifiers();
      return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers));
   }

   /**
    * Determine whether the given method is an "equals" method.
    * @see java.lang.Object#equals(Object)
    */
   public static boolean isEqualsMethod(Method method) {
      if (method == null || !method.getName().equals("equals")) {
         return false;
      }
      Class<?>[] paramTypes = method.getParameterTypes();
      return (paramTypes.length == 1 && paramTypes[0] == Object.class);
   }

   /**
    * Determine whether the given method is a "hashCode" method.
    * @see java.lang.Object#hashCode()
    */
   public static boolean isHashCodeMethod(Method method) {
      return (method != null && method.getName().equals("hashCode") && method.getParameterTypes().length == 0);
   }

   /**
    * Determine whether the given method is a "toString" method.
    * @see java.lang.Object#toString()
    */
   public static boolean isToStringMethod(Method method) {
      return (method != null && method.getName().equals("toString") && method.getParameterTypes().length == 0);
   }

   /**
    * Make the given field accessible, explicitly setting it accessible if
    * necessary. The <code>setAccessible(true)</code> method is only called
    * when actually necessary, to avoid unnecessary conflicts with a JVM
    * SecurityManager (if active).
    * @param field the field to make accessible
    * @see java.lang.reflect.Field#setAccessible
    */
   public static void makeAccessible(Field field) {
      if ((!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers()) ||
            Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) {
         field.setAccessible(true);
      }
   }

   /**
    * Make the given method accessible, explicitly setting it accessible if
    * necessary. The <code>setAccessible(true)</code> method is only called
    * when actually necessary, to avoid unnecessary conflicts with a JVM
    * SecurityManager (if active).
    * @param method the method to make accessible
    * @see java.lang.reflect.Method#setAccessible
    */
   public static void makeAccessible(Method method) {
      if ((!Modifier.isPublic(method.getModifiers()) || !Modifier.isPublic(method.getDeclaringClass().getModifiers()))
            && !method.isAccessible()) {
         method.setAccessible(true);
      }
   }

   /**
    * Make the given constructor accessible, explicitly setting it accessible
    * if necessary. The <code>setAccessible(true)</code> method is only called
    * when actually necessary, to avoid unnecessary conflicts with a JVM
    * SecurityManager (if active).
    * @param ctor the constructor to make accessible
    * @see java.lang.reflect.Constructor#setAccessible
    */
   public static void makeAccessible(Constructor<?> ctor) {
      if ((!Modifier.isPublic(ctor.getModifiers()) || !Modifier.isPublic(ctor.getDeclaringClass().getModifiers()))
            && !ctor.isAccessible()) {
         ctor.setAccessible(true);
      }
   }

   /**
    * Perform the given callback operation on all matching methods of the given
    * class and superclasses.
    * <p>The same named method occurring on subclass and superclass will appear
    * twice, unless excluded by a {@link MethodFilter}.
    * @param clazz class to start looking at
    * @param mc the callback to invoke for each method
    * @see #doWithMethods(Class, MethodCallback, MethodFilter)
    */
   public static void doWithMethods(Class<?> clazz, MethodCallback mc) throws IllegalArgumentException {
      doWithMethods(clazz, mc, null);
   }

   /**
    * Perform the given callback operation on all matching methods of the given
    * class and superclasses (or given interface and super-interfaces).
    * <p>The same named method occurring on subclass and superclass will appear
    * twice, unless excluded by the specified {@link MethodFilter}.
    * @param clazz class to start looking at
    * @param mc the callback to invoke for each method
    * @param mf the filter that determines the methods to apply the callback to
    */
   public static void doWithMethods(Class<?> clazz, MethodCallback mc, MethodFilter mf)
         throws IllegalArgumentException {

      // Keep backing up the inheritance hierarchy.
      Method[] methods = clazz.getDeclaredMethods();
      for (Method method : methods) {
         if (mf != null && !mf.matches(method)) {
            continue;
         }
         try {
            mc.doWith(method);
         }
         catch (IllegalAccessException ex) {
            throw new IllegalStateException("Shouldn't be illegal to access method '" + method.getName()
                  + "': " + ex);
         }
      }
      if (clazz.getSuperclass() != null) {
         doWithMethods(clazz.getSuperclass(), mc, mf);
      }
      else if (clazz.isInterface()) {
         for (Class<?> superIfc : clazz.getInterfaces()) {
            doWithMethods(superIfc, mc, mf);
         }
      }
   }

   /**
    * Get all declared methods on the leaf class and all superclasses. Leaf
    * class methods are included first.
    */
   public static Method[] getAllDeclaredMethods(Class<?> leafClass) throws IllegalArgumentException {
      final List<Method> methods = new ArrayList<Method>(32);
      doWithMethods(leafClass, new MethodCallback() {
         public void doWith(Method method) {
            methods.add(method);
         }
      });
      return methods.toArray(new Method[methods.size()]);
   }

   /**
    * Invoke the given callback on all fields in the target class, going up the
    * class hierarchy to get all declared fields.
    * @param clazz the target class to analyze
    * @param fc the callback to invoke for each field
    */
   public static void doWithFields(Class<?> clazz, FieldCallback fc) throws IllegalArgumentException {
      doWithFields(clazz, fc, null);
   }

   /**
    * Invoke the given callback on all fields in the target class, going up the
    * class hierarchy to get all declared fields.
    * @param clazz the target class to analyze
    * @param fc the callback to invoke for each field
    * @param ff the filter that determines the fields to apply the callback to
    */
   public static void doWithFields(Class<?> clazz, FieldCallback fc, FieldFilter ff)
         throws IllegalArgumentException {

      // Keep backing up the inheritance hierarchy.
      Class<?> targetClass = clazz;
      do {
         Field[] fields = targetClass.getDeclaredFields();
         for (Field field : fields) {
            // Skip static and final fields.
            if (ff != null && !ff.matches(field)) {
               continue;
            }
            try {
               fc.doWith(field);
            }
            catch (IllegalAccessException ex) {
               throw new IllegalStateException(
                     "Shouldn't be illegal to access field '" + field.getName() + "': " + ex);
            }
         }
         targetClass = targetClass.getSuperclass();
      }
      while (targetClass != null && targetClass != Object.class);
   }

   /**
    * Given the source object and the destination, which must be the same class
    * or a subclass, copy all fields, including inherited fields. Designed to
    * work on objects with public no-arg constructors.
    * @throws IllegalArgumentException if the arguments are incompatible
    */
   public static void shallowCopyFieldState(final Object src, final Object dest) throws IllegalArgumentException {
      if (src == null) {
         throw new IllegalArgumentException("Source for field copy cannot be null");
      }
      if (dest == null) {
         throw new IllegalArgumentException("Destination for field copy cannot be null");
      }
      if (!src.getClass().isAssignableFrom(dest.getClass())) {
         throw new IllegalArgumentException("Destination class [" + dest.getClass().getName()
               + "] must be same or subclass as source class [" + src.getClass().getName() + "]");
      }
      doWithFields(src.getClass(), new FieldCallback() {
         public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
            makeAccessible(field);
            Object srcValue = field.get(src);
            field.set(dest, srcValue);
         }
      }, COPYABLE_FIELDS);
   }


   /**
    * Action to take on each method.
    */
   public interface MethodCallback {

      /**
       * Perform an operation using the given method.
       * @param method the method to operate on
       */
      void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
   }


   /**
    * Callback optionally used to method fields to be operated on by a method callback.
    */
   public interface MethodFilter {

      /**
       * Determine whether the given method matches.
       * @param method the method to check
       */
      boolean matches(Method method);
   }


   /**
    * Callback interface invoked on each field in the hierarchy.
    */
   public interface FieldCallback {

      /**
       * Perform an operation using the given field.
       * @param field the field to operate on
       */
      void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
   }


   /**
    * Callback optionally used to filter fields to be operated on by a field callback.
    */
   public interface FieldFilter {

      /**
       * Determine whether the given field matches.
       * @param field the field to check
       */
      boolean matches(Field field);
   }


   /**
    * Pre-built FieldFilter that matches all non-static, non-final fields.
    */
   public static FieldFilter COPYABLE_FIELDS = new FieldFilter() {

      public boolean matches(Field field) {
         return !(Modifier.isStatic(field.getModifiers()) || Modifier.isFinal(field.getModifiers()));
      }
   };


   /**
    * Pre-built MethodFilter that matches all non-bridge methods.
    */
   public static MethodFilter NON_BRIDGED_METHODS = new MethodFilter() {

      public boolean matches(Method method) {
         return !method.isBridge();
      }
   };


   /**
    * Pre-built MethodFilter that matches all non-bridge methods
    * which are not declared on <code>java.lang.Object</code>.
    */
   public static MethodFilter USER_DECLARED_METHODS = new MethodFilter() {

      public boolean matches(Method method) {
         return (!method.isBridge() && method.getDeclaringClass() != Object.class);
      }
   };

}
